Many commenters applauded Musk for the gesture. One went so far as to call him Jesus Christ. But some criticized the Tesla CEO for his virtue signaling — and for his tweet, which they said seemed more like an encoded advertisement for Tesla than a genuine call to help.

Model S and X Teslas do indeed have a fancy air filtration system, which the company calls the "Bioweapon Defense Mode." The "Bioweapon Defense Mode" does not, in fact, protect against bioweapons, as Musk pointed out in a recent tweet. It does filter air particles. In other words, Teslas have built-in air purifiers.

Ostensibly, this is a useful feature for those who are affected by the poor air quality resultant of the wildfires. On Tuesday, Bay Area Air Quality Management District extended a red "unhealthy air" alert for much of the Bay Area, including San Francisco, Oakland and most of the North Bay. Officials urge residents to stay indoors.

The CEO has retweeted multiple Tesla owners who used laser particle counters to test the Bioweapon Defense Mode. One man shared photos of his "Windows Up/Windows Down" test. With the windows down, he recorded an Air Quality Index of 105 — considered "unhealthy for sensitive groups." With the windows up, the AQI was 2, or "good."